1. Field of the Invention
The present invention relates generally to inductors and, more particularly, to a system and method for producing an inductor with improved characteristics.
2. Description of the Related Art
FIGS. 7A and 7B illustrate a conventional layered-type inductor. This type of inductor is an example of a surface mounting type inductor. As illustrated in FIGS. 7A and 7B, the layered-type inductor is provided with a layered-type coil 52 formed by interconnecting a plurality of internal conductors 52a. The layered-type inductor also includes external electrodes 53a, 53b which are connected to respective end portions of the coil 52.
As illustrated in FIGS. 7A and 7B, such a layered-type inductor is commonly produced by laminating a plurality of ceramic green sheets 54 applied with internal conductors 52a having a predetermined pattern and formed via a printing method, connecting the internal conductors 52a via a hole 55 so as to form a coil, baking the coil, applying a conductor paste to a predetermined position of the element 51 and baking so as to form external electrodes 53a, 53b.
Since the internal conductor comprising the coil is provided via a printing method, it is difficult to have a thick internal conductor 52a (in general, 20 .mu.m is said to be the upper limit). As a result, the electric resistance of the internal conductor (coil) cannot be lower than a certain level.
In order to solve this problem, an inductor, as illustrated in FIG. 8, has been introduced. This inductor comprises an internal conductor 62 prepared by forming a coil with a metal wire (such as an Ag wire) surrounded by an element 61 made from a ceramic material. The inductor also comprises external electrodes 63a, 63b provided in the element 61. However, since the ceramic element 61 and the internal conductor 62 are closely contacted, stress is generated therebetween due to the contraction difference between the ceramic 61 and the internal conductor 62 at the time of baking. This stress generates cracks in the ceramic. One skilled in the art will appreciate that stress can remain in the inductor even when cracks are not generated. Furthermore, stress can also be generated due to the contraction difference between the ceramic and the internal conductor as a result of a temperature change due to the surrounding environment or the usage condition.
The stress that remains in the inductor and the stress generated by the usage condition, as mentioned above, not only deteriorate the electric characteristics of the inductor, but may also generate cracks in the ceramic, depending upon the size of the stress. Moreover, repetition of application and release of stress also serves as the cause of crack generation in the ceramic. Crack generation leads to an increase in the leakage flux which further deteriorates the characteristics of the inductor.